It is our aim to subject to genetic and biochemical analysis two syndromes relevant to aging. Our approach will combine the methods of somatic cell genetics, recombinant DNA cloning, and restriction endonuclease analysis. The syndromes to be studied are xeroderma pigmentosum and Werner's syndrome. We selected express specific phenotypes at the cellular level in vitro. We have already begun work on XP, and it will serve as a guide to our subsequent analysis of WS. These experiments reveal that the XP defect in complementation group A can be repaired by transferring mouse chromosomes into the defective, human cells. We have also shown that resistance to UV irradiation can be used as a selective method for hybrid recovery. Therefore, it is now possible to map the murine genome which complements XP-A. The same analysis will be applied to other XP complementation groups. The experiments will provide evidence for the existence of multiple, unlinked loci governing XP expression, or a single complex locus. In other experiments, which combine SCG methodologies with modern biochemical techniques, we will map and isolate the genes for human XP and WS. The human genes will be isolate by first purifying the relevant mRNA using a single cell bioassay based on microinjection. Purified mRNA will be reverse transcribed and then cloned using a recombinant DNA approach. Identification of XP and WS specific clones will be accomplished by abrogation of the microinjection bioassay. Resulting XP and WS probes will be used to map the endogenous genes by a combined SCG and Southern blotting procedure which we have already developed. It is our hope that these studies will provide specific information of value for XP, WS, and serve as a model for the future analysis of additional genes relevant to the aging process.